linux-kernel - Re: [PATCH 2/3 v3] iommu/fsl: Add iommu domain attributes required by fsl PAMU driver.

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Date:	Mon, 22 Oct 2012 17:05:31 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Varun Sethi <Varun.Sethi@...escale.com>
CC:	<joerg.roedel@....com>, <iommu@...ts.linux-foundation.org>,
	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	Varun Sethi <Varun.Sethi@...escale.com>
Subject: Re: [PATCH 2/3 v3] iommu/fsl: Add iommu domain attributes required
 by fsl PAMU driver.

On 10/17/2012 12:32:49 PM, Varun Sethi wrote:
> Added the following domain attributes required by FSL PAMU driver:
> 1. Subwindows field added to the iommu domain geometry attribute.
> 2. Added new iommu stash attribute, which allows setting of the
>    LIODN specific stash id parameter through IOMMU API.
> 3. Added an attribute for enabling/disabling DMA to a particular
>    memory window.
> 
> Signed-off-by: Varun Sethi <Varun.Sethi@...escale.com>
> ---
> change in v3:
> -renamed the stash attribute targets
> 
>  include/linux/iommu.h |   35 +++++++++++++++++++++++++++++++++++
>  1 files changed, 35 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index f3b99e1..c3b9d73 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -44,6 +44,33 @@ struct iommu_domain_geometry {
>  	dma_addr_t aperture_start; /* First address that can be  
> mapped    */
>  	dma_addr_t aperture_end;   /* Last address that can be  
> mapped     */
>  	bool force_aperture;       /* DMA only allowed in mappable  
> range? */
> +
> +	/* The subwindows field indicates number of DMA subwindows  
> supported
> +	 * by the geometry. Following is the interpretation of
> +	 * values for this field:
> +	 * 0 : This implies that the supported geometry size is 1 MB
> +         * with each subwindow size being 4KB. Thus number of  
> subwindows

Whitespace

> +	 * being = 1MB/4KB = 256.
> +	 * 1 : Only one DMA window i.e. no subwindows.
> +	 * value other than 0 or 1 would indicate actual number of  
> subwindows.
> +	 */

This language is way too specific for the generic geometry struct  
(especially when you start talking about specific sizes).  Please  
explain in implementation-neutral terms what this field means.

> @@ -60,6 +87,14 @@ struct iommu_domain {
>  enum iommu_attr {
>  	DOMAIN_ATTR_MAX,
>  	DOMAIN_ATTR_GEOMETRY,
> +	/* Set the IOMMU hardware stashing
> +	 * parameters.
> +	 */
> +	DOMAIN_ATTR_STASH,
> +	/* Explicity enable/disable DMA for a
> +         * particular memory window.
> +         */
> +	DOMAIN_ATTR_ENABLE,
>  };

Whitespace

-Scott
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